1. Field of Invention
This invention relates to a material delivery/removal system for transporting grain, cement, and other stored materials from a storage bin, dome or other lateral enclosure. More specifically, the present invention relates to a bulk material delivery system which includes a movement or torque assist device for use with a rotating drag arm for pulling the bulk material toward a central outlet.
2. Prior Art
Bulk storage of materials such as grain, cement, dry fuels and other commodities poses many problems which ultimately affect the availability of food, fuels and construction materials upon which each nation's economy depends. These problems range from storage requirements to special handling needs in material transport. The most difficult challenges typically arise when the bulk materials require both a controlled storage environment and unique handling profile during loading and unloading in storage areas.
Such materials include cement and similar bulk commodities which must be stored in a protected atmosphere. Because such materials require total enclosure for protection from the elements, convenient access for retrieval is typically limited. Although movable roofing permits direct use of scoop shovels and buckets to raise the bulk material to nearby trucks or rail cars, such facilities and methods are labor intensive and require a significant capital investment for equipment and special construction of buildings. As a consequence, industrial trends have focused on reducing the cost of storage and handling by simplifying construction of storage areas.
For example, free-standing dome structures have combined economical construction with the benefits of total enclosure. U.S. Pat. No. 3,456,818 illustrates a dome structure used for storing grains. Bulk materials are loaded Within the dome through a top opening and are distributed outward by a rotating auger or drag arm that drags the grain outward toward the laterally enclosing dome wall. This auger is designed to rotate along its longitudinal axis on top of the grain, as well as rotate radially around a center support post to provide redistribution of grain across the 360 degree top surface area of the grain. This dual rotation of the auger functions to maintain the auger in a "floating" configuration on top of the grain storage surface. The weight of the auger is carefully selected to enhance this floating performance as a necessary part of the system.
Outloading is accomplished by rotation of the center support post without the need for rotation of the auger about its longitudinal axis. An outlet port is formed in a floor surface below the support post and includes a subfloor auger which acts as a conveyer to transport material as it drops by gravity flow from the interior of the dome. Once the grain has reached its natural declination of flow toward the central outlet port, the auger is activated to drag the remaining grain toward the center. Eventually, the total contents of the dome can be swept to the outlet port as the rotating auger cycles to a horizontal orientation near the floor surface.
Although the dome storage structure with transport system was invented approximately 25 years ago, it has experienced only limited commercial success. Its apparent limitation for use with bulk materials having physical properties similar to grains also inhibits its utility in other demanding storage needs such as with cement and other dry goods which are subject to greater compaction. These latter materials will naturally congeal to a rigid mass under the weight of the stored upper layers. This rigid mass is very difficult to break up and effectively blocks gravity flow of stored materials into the outlet. Because the auger assembly is designed to float on top of the grain, it has no significant influence on desired subsurface material movement.
In view of the numerous problems with the referenced dome storage system, access for movement of stored materials has generally been provided by lateral doors or openings at the base of the dome. These doors are opened and permit front-end loaders to use conventional loading techniques with scoop buckets or similar equipment to transport the materials. Unfortunately, highly compacted commodities such as cement do not readily collapse with removal of under support material. Indeed, a front-end loader may form a cavern opening of considerable size within the rigid base layer of material which could collapse without warning, causing potentially fatal results.
Earlier patents of this same inventor as represented by U.S. Pat. Nos. 5,098,247 and 5,180,272 and European patent application PCT/US/03080, filed Apr. 15, 1992 disclose an improved system for outloading bulk materials which utilizes a rotating auger which moves from a vertical orientation, sequentially to a horizontal position to complete removal. A significant problem with the use of such a mechanism arises because of the increased moment arm required to rotate the extended auger as the center of mass continues to displace from the vertical support column. Normal design criteria dictates that the power rating of the drive motor be selected to meet the peak power demand which occurs when the auger is in a near horizontal orientation. Alternatively, a more extensive gear box or transmission system may be incorporated to provide the increased power requirement. Unfortunately, the increased power requirement and or gearing system adds substantial expense to the overall system cost.
The increased load required by the greater moment arm is further compounded by resistance offered by the compacted bulk material which is to be removed. These two problems compound each other because as the moment arm increases with greater declination of the auger, the compaction of the material also increases because of the increased weight of overhead materials. Therefore, by the time the auger reaches the near horizontal position in rotation, the worst conditions exist. Specifically, the auger is in its most extended orientation and the material is at maximum compaction because this material has born the weight of the total material above.
The problem of increased compaction also arises with traditional storage structures. For example, U.S. Pat. No. 2,711,814 discloses an auger useful for cleaning flat bottoms of a grain tank. Related auger transport devices have been used in silo storage systems, such as disclosed in U.S. Pat. Nos. 2,500,043; 3,755,918; 3,155,247 and 3,438,517. These patents are representative of a broad range of applications for the transport properties of an auger within a grain bin. Experience has shown that such an auger system is not likely to be practical with respect to bulk materials which experience greater compaction, forming a rigid base layer. It is perhaps for this reason that much of the prior art technology utilizing an auger transport system is directed toward grains and other bulk materials which have less tendency to compact under pressure. The more flowable condition of these grains enables the outloading in conventional storage bins by mere gravity flow.
The auger transport system in these disclosures functions primarily to redistribute bulk material toward the center of the storage bin to keep gravity flow in process throughout the outloading procedure. They are not generally intended to be responsive to changing compaction conditions that occur as the rotating auger progresses toward the bottom of the bin. In the latter case, conventional design criteria would again dictate that greater power would be provided by increased motor power and/or an improved transmission system.
Several patents disclose devices for providing torque assist to the rotating arm or auger. For example, U.S. Pat. No. 1,550,311 by Foster illustrates a rotating drum having closely positioned grooves or teeth to urge the rotating arm along its rotating path. Because of the close proximity of the teeth, further compaction by the rotating drum is disturbed by the movement action caused by the teeth themselves. Such a configuration severely limits the ability of the rotating drum to operate with respect to heavily compacted materials. U.S. Pat. No. 2,711,814 by McCarthy illustrates the use of a rotating wheel which rotates with the auger when in the horizontal position. This wheel is primarily for the purpose of supporting the shaft at floor level and does not offer significant torque assist when suspended on the compacted material. U.S. Pat. No. 3,451,566 by Hansen illustrates the use of a crawler-type device which appears to have open track elements for engaging a top surface of the stored material to push the rotating augers about their circular path. Hereagain, the crawler type device does not appear to be configured to enhance the ability of the compacted surface by minimizing disturbance of this compacted material. To the contrary, the close proximity of the track elements and the absence of a compacting surface associated with the track elements suggest that as each track element penetrates the storage material, it will loosen and reduce the resistance offered by surrounding compaction material with respect to the next blade to be engaged. This loosened material then offers less ability to advance the crawler-type drive unit. Although this may be suitable for silage in a frozen condition, its application to broader varieties of compacted materials is limited. Finally, U.S. Pat. No. 3,794,190 by Lambert, Jr. discloses the use of outer drive wheels for turning the rotating augers, but without engaging the compacted material as the drive surface. Rather, such units utilize a circular ring gear which engages a rotating sprocket positioned above the stored material.
None of these references resolve the problem of loss of traction between the blades or teeth of the rotating wheel or track and the stored material. Indeed, the disclosed torque assist devices have an array of teeth or track elements which are closely positioned and otherwise configured to disturb the compacted material. This disturbed or loosened material has less ability to resist movement and a weakened resistance force to push the torque assist device and attached drag arm in a desired forward or rearward direction.